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| United States Patent |
5,116,713
|
|
Uchida
, et al.
|
May 26, 1992
|
Toner for developing latent electrostatic image
Abstract
The improved toner for development of a latent electrostatic image contains
as a binder a polyester obtained by polycondensation reaction of a monomer
composition containing the specified components and it also contains an
acid-modified polypropylene. This toner exhibits satisfactory fixability,
developing quality, transferability, cleanability, as well as good
resistance to agglomeration and toner fusion.
| Inventors:
|
Uchida; Masafumi (Hachioji, JP);
Yajima; Toshiko (Hachioji, JP);
Takagiwa; Hiroyuki (Hachioji, JP);
Takahashi; Jiro (Hachioji, JP)
|
| Assignee:
|
Konica Corporation (Tokyo, JP)
|
| Appl. No.:
|
552763 |
| Filed:
|
July 16, 1990 |
Foreign Application Priority Data
| Current U.S. Class: |
430/108.8; 430/109.4; 430/111.4 |
| Intern'l Class: |
G03G 009/087 |
| Field of Search: |
430/109,110
|
References Cited
U.S. Patent Documents
| 4100087 | Jul., 1978 | Takayama et al. | 430/108.
|
| 4265992 | May., 1981 | Kouchi et al. | 430/109.
|
| 4804622 | Feb., 1989 | Tanaka et al. | 430/109.
|
| 4939059 | Jul., 1990 | Kawabe et al. | 430/109.
|
Primary Examiner: Goodrow; John
Attorney, Agent or Firm: Bierman; Jordan B.
Claims
What is claimed is:
1. A toner for development of a latent electrostatic image that contains as
a binder a polyester having a ratio of hydroxyl group value (OHV) to acid
value (AV) not exceeding 1.2 obtained by polycondensation reaction of a
monomer composition containing the components (1)-(3) described below and
which also contains a polypropylene modified with a carboxylic acid or an
acid anhydride thereof:
component (1): a polyvalent monomer having a valence of 3 or more;
component (2): an aromatic dicarboxylic acid; and
component (3): a dialcohol containing at least 70 mol % of aliphatic
dialcohol.
2. A toner according to claim 1 wherein the sum of acid value (AV) and
hydroxyl group value (OHV) of said polyester is in the range of 20-80.
3. A toner according to claim 1 wherein said component (1) is selected from
the group consisting of esters and anhydrides of benzene tricarboxylic
acid.
4. A toner according to claim 1 wherein said acid-modified polypropylene
has an acid value of 1-100.
5. A toner according to claim 1 wherein said acid-modified polypropylene
has a hardness of at least 42.
6. A toner according to claim 1 wherein said component (1) is an aromatic
polyvalent carboxylic acid having a valence of 3 or more.
7. A toner according to claim 6 wherein said aromatic polyvalent carboxylic
acid is a benzenetricarboxylic acid.
8. A toner according to claim 1 wherein component (1) occupies 1-30 mol %
of the monomer composition.
9. A toner according to claim 1 herein component (2) is selected from the
group consisting of phthalic acid, isophthalic acid, terephthalic acid,
and anhydrides or esters thereof.
10. A toner according to claim 1 wherein component (3) has 2-10 carbon
atoms.
11. A toner according to claim 10 wherein at least 50 mol % of all the
aliphatic dialcohols used as component (3) is occupied by an aliphatic
dialcohol having a branched chain.
12. A toner according to claim 1 wherein said polyester has a softening
point of 90.degree.-170.degree. C.
13. A toner according to claim 1 wherein said polyester has a glass
transition point of 50.degree.-70.degree. C.
14. A toner according to claim 1 wherein said acid-modified polypropylene
has a softening point of 100.degree.-160.degree. C.
15. A toner according to claim 1 wherein said acid-modified polypropylene
has a melt index of no more than 104 poises.
16. A toner according to claim 1 wherein said acid-modified polypropylene
is incorporated in an amount of 1-20 parts by weight per 100 parts by
weight of the binder.
17. A toner according to claim 1 which contains a colorant.
18. A toner according to claim 1 which has an inorganic or organic fine
particulate matter added externally.
Description
BACKGROUND OF THE INVENTION
This invention relates to an agent for developing a latent electrostatic
image formed on the surface of photoreceptors used in electrophotography,
electrostatic recording, electrostatic printing and other reprographic
methods.
Production of visible images from image information of interest is commonly
accomplished by methods that involve the formation of latent electrostatic
images, such as electrophotography, electrostatic recording and
electrostatic printing. In electrophotography, a uniform static charge
layer is first provided on the surface of a photoreceptor having a
light-sensitive layer made of a photoconductive material. By subsequent
imagewise exposure, a latent electrostatic image corresponding to the
illuminated original is formed on the surface of the photoreceptor and
then developed with a developer to form a toner image. The toner image is
transferred onto a recording material such as paper and thereafter fixed
by heating or pressure application to produce a copy image. After the
transfer step, the photoreceptor is flooded with light to neutralize any
residual charges and the toner image remaining on the photoreceptor is
wiped off to condition the photoreceptor for another image cycle.
In order to insure that a copy image of high density without fog is formed
over many cycles in a consistent way, the triboelectric charge on the
toner particles must always be within an appropriate range. To this end,
it is essential that fouling of the triboelectricity providing material or
member (e.g. carrier or doctor blade) or the developer transport medium by
the toner material be effectively prevented. Further, the fouling of the
photoreceptor by the toner material must be prevented in order to insure
an effective potential creation.
From the viewpoints of cleaning efficiency and durability, the toner that
remains on the photoreceptor after the transfer step is preferably wiped
off by means of cleaning with a doctor blade. However, the finer the
particles of the toner that remains on the photoreceptor, the greater the
force of relative adhesion to the photoreceptor and the more difficult it
becomes to wipe off the toner. To prevent this problem of "insufficient
cleaning", the toner is required to have good cleanability.
The toner image is preferably fixed by means of a hot pressure roll since
it provides high heat efficiency and is capable of high-speed fixing.
However, the use of a hot pressure roll as a fixing means has the
disadvantage that "offsetting", a phenomenon in which part of the toner
powder in the toner image being fixed is transferred onto the surface of
the roll and is then transferred onto the recording material being sent in
the next image cycle, whereby the final image is fouled. In order to
prevent this trouble, the toner must have good anti-offsetting quality.
In continuous image formation, a substantial amount of heat is transferred
to the recording material and the temperature of the hot pressure roll has
a great tendency to drop, thus increasing the chance of the recording
material of sticking to the surface of the roll. Thus, the toner is also
required to have high resistance to this problem of "sticking".
With a view to satisfying the requirements described above, particularly
anti-offsetting and anti-sticking qualities, it has already been proposed
that a crosslinked polyester (Unexamined Published Japanese Patent
Application No. 37353/1982) be used in combination with an incorporated
low-molecular weight polypropylene (hereinafter abbreviated as PP; see
Unexamined Published Japanese Patent Application No. 65231/1974) in
toners. However, at high copying speeds or in small developing and
cleaning devices, the combination of a polyester and a polypropylene has
been found to be unsatisfactory since (1) the fluidity and agglomeration
of toner particles is low and (2) the toner has a tendency to fuse to the
triboelectricity providing material or member or the photoreceptor. This
may be explained as follows: highly polar polyesters that have high
contents of an ester group
##STR1##
a carboxyl group (--COOH) and a hydroxy group (--OH) inherently have a
very small force of interfacial adhesion to the nonpolar polypropylene, so
that in the process of toner production, particularly in the pulverizing
and classifying steps, fine particles of polypropylene (10-30 .mu.m) are
formed to cause the problems (1) and (2) mentioned above. In addition, the
dissociation of polypropylene is accelerated under the impact of
compression by the cleaning blade or agitation in various pipes.
In an attempt to solve these problems, it has been proposed that
polypropylene be oxidized or acid-modified to introduce carboxyl or
hydroxy groups (see Unexamined Published Japanese Patent Application Nos.
54348/1983, 129863/1984, 226160/1987 and 229159/1987). However, this
approach has had the following disadvantages:
a. A solid black image at the leading edge of the recording material has a
great tendency to stick to the surface of a hot pressure roll;
1) combinations of acid-modified PP and common polyesters (PEs) as taught
in Unexamined Published Japanese Patent Application Nos. 54348/1983,
229159/1987 and 226160/1987 have such a good miscibility between the
components that phase separation does not readily occur in the fixing
step, and this reduces the efficiency of paper release. This problem is
particularly noticeable with a solid black image at the leading edge of
paper and has been the major cause of troubles such as jamming in the
fixing step;
2) the combination of an acid-modified PP and a polyester of bisphenol A
type (Unexamined Published Japanese Patent Application No. 129863/1984) is
a typical example of the case where the problem described in (1) is most
likely to occur.
b. Fine toner particles will readily form in the developing device to
impair developing, transfer and cleaning qualities;
1) methods are available that use acid-modified PPs that are highly
miscible with polyesters in order to provide improved toner fluidity,
agglomeration and resistance to fusion (inclusive of filming to the
photoreceptor) (see Unexamined Published Japanese Patent Application Nos.
29159/1987 and 226160/1987), but polyester resins themselves are brittle
and have a tendency to disintegrate to form fine toner particles in the
developing device as the copying cycle is repeated; as a result, the
relative adhesion between the triboelectricity providing material or
member and the toner and that between the photoreceptor and the toner will
increase to cause deterioration in developing, transfer and cleaning
qualities; further, the fine toner particles will fuse to the
triboelectricity providing material or member in copying cycles, whereby
the charging ability of said material or member is reduced; and
2) the already described combination of an acid-modified PP and a polyester
of bisphenol A type (Unexamined Published Japanese Patent Application No.
129863/1984) is again a typical example of the case where the problem just
described above in (1) is most likely to occur.
SUMMARY OF THE INVENTION
An object, therefore, of the present invention is to provide a toner that
does not permit a solid black image at the leading edge of a recording
material to stick to a hot pressure roll and which has high resistance to
offsetting.
Another object of the present invention is to provide a toner that has good
developing, transfer, cleaning and anti-agglomeration qualities and which
is effectively protected against fusion to the triboelectricity providing
material or member.
In order to attain these objects of the present invention, it is important
that (1) and acid-modified PP be dispersed as fine particles in a solid
state and readily undergo phase separation from a polyester during fixing
(by heating or pressure application) and that (2) the resin itself will
not form fine particles in the developing and cleaning devices.
As regards the polyester, our intensive studies have revealed the
following: (1) introducing a short-chain monomer is effective for the
purpose of increasing the concentration of ester groups in the resin to
thereby increase the solubility parameter; and (2) introducing an
aliphatic alcohol is effective in increasing the flexibility of the
polymer sequence composed of said monomer.
The above-stated objects of the present invention can be attained by a
toner for development of a latent electrostatic image that contains as a
binder a polyester obtained by polycondensation reaction of a monomer
composition containing the components (1)-(3) described below and which
also contains PP modified with a carboxylic acid or an acid anhydride
thereof:
component (1): a polyvalent monomer having a valance of 3 or more;
component (2): an aromatic dicarboxylic acid;
component (3): an aliphatic dialcohol.
The polyester resin containing these components (1)-(3) may well be
considered to be a binder that is optimum for use in combination with a
carboxylic acid modified PP.
The acid value (AV) and the hydroxyl group value (OHV) of the polyester
resin may be used as criteria for selecting an appropriate polyester resin
to be combined with the acid-modified PP, and particularly preferred
polyester resin is such that the sum of AV and OHV is in the range of
20-80.
The term "acid value" (AV) as used herein means the number of milligrams of
the potassium hydroxide necessary to neutralize the acid contained in 1 g
of the sample of polyester resin. The term "hydroxyl group value" (OHV)
means the number of milligrams of the potassium hydroxide necessary to
neutralize the acetic acid that binds to the hydroxyl group when it is
used to acetylate 1 g of the polyester sample in accordance with "Standard
Methods for Analysis and Testing of Fats and Oils" (compiled by the Japan
Oil Chemists Society).
The sum of AV and OHV in a polyester means the number of terminal groups in
the molecular chain of the polymer and this value has a great effect on
the dispersion of the acid-modified PP. A polyester in which the value of
AV +OHV ranges from 20 to 80 has good miscibility with the acid-modified
PP, so that the toner in a solid state will form a fine dispersion whereas
it will undergo rapid phase separation during fixing.
We have also found that not only the sum of terminal groups in the polymer
chain but also their proportions are important for the miscibility of the
polyester with the acid-modified PP. From this viewpoint, it is preferred
to select a polyester that has an OHV to AV ratio of no more than 2.0,
with the OHV/AV value of less than 1.2 being more preferred. A polyester
in which the value of OHV/AV is no more than 2.0, preferably less than
1.2, has a tendency to retard self-curing during mixing and hence is
capable of maintaining an adequate melt viscosity in such a way that the
acid-modified PP forms a uniform fine dispersion whereas it undergoes
rapid phase separation during fixing.
We have also found that the acid value of the acid-modified PP is a
parameter that is important for attaining even better miscibility with the
polyester specified above. The preferred acid value is in the range of
1-100, with the range of 6-50 being particularly preferred. For the
purpose of providing even better cleaning and anti-fusion qualities, the
acid-modified PP preferably has a penetration degree of less than 2, more
preferably 1 or below. The degree of penetration is measured by the method
described in JIS K 2235 (1980).
For the same reasons as described above, the acid-modified PP preferably
has a hardness of at least 42 and a compressive failure stress of at least
40 kg/cm.sup.2. The hardness is measured with an "Askar" rubber hardness
meter (product of Kobunshi Keiki Co., Ltd.) by the method described in
ASTM D 2240-68. The compressive failure stress is measured with an
Autograph IS-5000 of Shimadzu Corp. under the conditions described below
in accordance with JIS K 7208 (1975):
(1) shape of the sample: rectangular prism (15.0 mm.times.12.0
mm.times.37.0 mm)
(2) test speed: 10 mm/min
(3) measurement temperature: 25.degree. C.
(4) method of preparing the specimen:
i) put a powder sample into a mold having inside dimensions of 15.0
mm.times.12.0 mm.times.37.0 mm;
ii) heat the powder in a forced-air circulation dryer to a temperature that
is about 10.degree. C. above the softening point of the sample, so that it
is melted and defoamed;
iii) supply an additional portion of the sample to fill the gap in the mold
formed by defoaming, and remelt it; repeat this procedure until the mold
is completely filled with the sample;
iv) cool the melted and defoamed sample slowly to room temperature over
several hours; and
v) take the sample out of the mold, shave its surface to prepare a
measurement specimen in rectangular prism form having the dimensions of
15.0 mm.times.12.0 mm.times.37.0 mm.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a monomer composition containing components
(1)-(3) described above is subjected to polycondensation reaction and the
resulting polyester (hereinafter sometimes referred to as "the specified
polyester") is used as a binder resin.
Examples of the polyvalent monomer having a valence of 3 or more which is
used as component (1) include: 1,2,4-benzenetricarboxylic acid,
1,3,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid,
2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid,
1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid,
1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane,
tetra(methylenecarboxy)methane, 1,2,7,8-octanetetracarboxylic acid, enpole
trimer acid, as well as anhydrides and esters of these acids.
Among these polyvalent monomers, aromatic polyvalent carboxylic acids are
particularly preferred for the purpose of preparing the polyester of the
present invention which contains an aliphatic dialcohol as component (3).
More preferred are benzenetricarboxylic acids such as benzenetricarboxylic
acid and anhydrides or esters thereof since they are capable of providing
triboelectricity in a consistent manner.
Polyesters containing aliphatic dialcohols have much fewer .pi. electrons
than conventional polyesters containing bisphenolic alcohols and, hence,
the rise speed of the electrification of such polyesters will often
decrease. However, it is assumed that this problem can be prevented by
selecting component (1) from among benzenetricarboxylic acids such as
benzenetricarboxylic acid and anhydrides or esters thereof.
Component (1) is preferably incorporated in an amount of 1-30 mol % of the
total amount of the monomer composition. The formation of fine toner
particles can be prevented in a particularly effective way by using a
polyester containing component (1) in an amount within the above-specified
range. A more preferred range is from 1 to 15 mol % of the total amount of
the monomer composition.
Examples of the aromatic dicarboxylic acid used as component (2) include
phthalic acid, isophthalic acid, terephthalic acid, as well as anhydrides
and esters of these acids.
Such aromatic dicarboxylic acids may be used in combination with other
dicarboxylic acids including, for example, maleic acid, fumaric acid,
mesaconic acid, citraconic acid, itaconic acid, glutaconic acid,
cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid,
malonic acid, anhydrides or loweralkyl esters of these acids, dimers of
linolenic acid, and other bifunctional organic acid monomers. These
dicarboxylic acids are preferably incorporated in amounts of no more than
30 mol % of the total content of dicarboxylic acids.
In order to provide a toner that is more effectively protected against the
fusion of fine toner particles to the triboelectricity providing material
or member, the aliphatic dialcohol as component (3 ) preferably contains
2-10 carbon atoms. If the number of carbon atoms in the aliphatic
dialcohol is less than 2, the molecular chain of the polyester will have
only limited flexibility. If the number of carbon atoms exceeds 10, the
molecular chain of the polyester will have sufficient flexibility to
prevent the formation of fine particles but, on the other hand, the toner
will readily undergo plastic deformation on the triboelectricity providing
material or member, whereby the chance of toner fusion to said material or
member is increased.
In order to insure that the formation of fine toner particles is prevented
in a more effective way, it is preferred that the content of an aliphatic
dialcohol having branched chains is at least 50 mol % of all the aliphatic
alcohols used as component (3). The term "branched chains" as used herein
means carbon chains other than the linear backbone chain that is formed of
carbon atoms connected between two OH groups, as illustrated below:
##STR2##
If an aliphatic dialcohol having such branched chains occupies at least 50
mol % of all the aliphatic dialcohols used as component (3), water that is
to adsorb on the ester bond in the polyester is blocked by the alkyl
chain, whereby the resulting water absorption is sufficiently reduced to
achieve effective protection against deterioration in a moist atmosphere.
Specific examples of the aliphatic dialcohol that can be used as component
(3) are listed below:
1) aliphatic dialcohols having branched chains such as propylene glycol
(1,2-propanediol), 1,2-butanediol, 1,3-butanediol, 2,3-butanediol,
neopentyl glycol, 3-methylpentane-1,3,5-triol, 1,2-hexanediol,
2,5-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol and
2-ethyl-1,3-hexanediol; and
2) aliphatic dialcohols having no branched chains, such as ethylene glycol,
1,3-propanediol, 1,4-butanediol, diethylene glycol, 2-butene-1,4-diol,
1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, triethylene glycol,
tetraethylene glycol, tripropylene glycol, and pentaethylene glycol.
These aliphatic dialcohols may be used in combination with other dialcohols
including, for example, 1,4-bis(hydroxymethyl)-cyclohexane, bisphenol A,
hydrogenated bisphenol A, etherized bisphenols (e.g. polyoxyethylenated
bisphenol A and polyoxypropylene bisphenol A), and other bifunctional
alcoholic monomers. These dialcohols are preferably incorporated in
amounts of no more than 30 mol % of all the dialcohols used. If the
proportions of such "other dialcohols" are excessive, the flexibility of
the molecular chain of the polyester resin is insufficient to prevent the
formation of fine toner particles, whereby the durability of the developer
is impaired.
The specified polyester preferably has a softening point (Tsp) of
90.degree.-170.degree. C., with the range of 100.degree.-160.degree. C.
being more preferred. If the Tsp of the specified polyester is too low,
the toner powder is highly likely to break into finer particles, which
increases the chance of toner fusion to the surface of a triboelectricity
providing material or member. Further, the anti-offsetting quality of the
toner is also impaired. If, on the other hand, the Tsp of the specified
polyester is excessive, its miscibility with the acid-modified PP will
decrease to increase the chance of fouling of the triboelectricity
providing material or member.
The softening point Tsp of the specified polymer can be measured and
defined as follows: using a Kohka-type flow tester Model CFT-500 of
Shimadzu Corp., a measurement is performed on a sample in an amount of 1
cm.sup.3 ( in weight expressed by the true specific gravity times 1
cm.sup.3) under a load of 20 kg/cm.sup.2 with a nozzle of 1 mm.phi. and 1
mm.sup.L at a heating rate of 6.degree. C./min after preheating at
80.degree. C. for 10 min; if the S portion of the resulting curve that
plots temperature against the amount of drop of the plunger in the flow
tester has a height h, then the temperature at the point h/2 is defined as
the Tsp of the sample.
The specified polyester preferably has a glass transition point Tg of
50.degree.-70.degree. C. The glass transition point Tg as used herein can
be measured and defined as follows: using a diffraction scanning
calorimeter "Low-Temperature DSC" of Rigaku Denenki Co., Ltd., 1) put a
30-mg powder sample into an aluminum pan and heat from 20.degree. C. to
100.degree. C. at a rate of 10.degree. C./min; 2) leave the sample at
100.degree. C. for 3 min and thereafter cool with air to 20.degree. C.; 3)
and perform measurements with the temperature being elevated at a rate of
10.degree. C./min; the temperature at the point where an extension of the
base line below the glass transition point on the DSC thermogram in the
glass transition region crosses the tangential line that has a maximum
gradient in the region from the rising edge of the peak to its apex is
defined as the Tg of the sample.
The toner of the present invention for development of a latent
electrostatic image has not only the above specified polyester (i.e.
binder) but also an acid-modified PP. The number average molecular weight
(Mn) of the acid-modified PP is preferably in the range of 500-20,000 in
order to provide a good cleaning quality and to prevent a solid black
image at the leading edge of a recording material from sticking to a hot
pressure roll. A more preferred range of Mn is from 1,000 to 10,000.
The softening point of the acid-modified PP corresponds to its molecular
weight and is preferably within the range of 100.degree.-160.degree. C.
For the purpose of preventing a solid black image at the leading edge of a
recording material from sticking to a hot pressure roll, the acid-modified
PP preferably has a melt viscosity not higher than 10.sup.4 poises, more
preferably not higher than 5.times.10.sup.3 poises. The density of the
acid-modified PP is closely related to its hardness and should preferably
be at least 0.85 g/cc in order to provide good cleaning and anti-fusion
qualities.
The number average molecular weight (Mn) of the acid-modified PP is
determined by either GPC or a vapor permeation method. Measurements of its
softening point and density are performed in accordance with JIS K 2531
(1960) and JIS K 6760 (1966), respectively. The melt viscosity is
represented as a value at 160.degree. C. and measured with a Brookfield
viscometer.
The acid-modified PP described above is preferably incorporated in an
amount of 1-20 parts by weight per 100 parts by weight of the binder. If
the proportion of the acid-modified PP is unduly small, the
anti-offsetting and anti-sticking qualities of the toner will often
deteriorate. If, on the other hand, the proportion of the acid-modified PP
is excessive, macro-agglomerates will form in the polyester to increase
the chance of fouling of the triboelectricity providing material or
member.
The toner of the present invention for development of a latent
electrostatic image may optionally contain additives such as colorants and
charge control agents. Illustrative colorants include: carbon black,
nigrosine dye (C.I. No. 50415B), aniline blue (C.I. No. 50405), chalcoil
blue (C.I. No. azoic Blue 3), chrome yellow (C.I. No. 14090), ultramarine
blue (C.I. No. 77103), Du Pont oil red (C.I. No. 26105), quinoline yellow
(C.I. No. 47005), methylene blue chloride (C.I. No. 52015), phthalocyanine
blue (C.I. No. 74160), malachite green oxalate (C.I. No. 42000), lamp
black (C.I. No. 77266), rose bengal (C.I. No. 45435), and mixture thereof.
Colorants containing magnetic materials may also be used. These colorants
are preferably incorporated in amounts of 1-20 parts by weight per 100
parts by weight of the binder.
Acidic carbon blacks having a pH of 6.5 and below have particularly good
dispersibility in the specified polyester, and a desired dispersion of the
acid-modified PP is insured without causing substantial agglomeration.
Known charge control agents may also be added to the toner of the present
invention as required.
Further, known inorganic fine particulate matters such as silica and
titanium oxide, or organic fine particulate matters such as polymethyl
methacrylate and silicone resin may be externally added to the toner of
the present invention as required.
While the toner of the present invention can be produced by any process,
the following method may be applied with advantage: 1) mixing the above
specified polyester with the acid-modified PP and any other toner
components that are added as required; 2) melting and kneading the
mixture; 3) cooling the melt; 4) pulverizing the cooled product; and 5)
classifying it to obtain a toner having a desired average particle size.
If the toner of the present invention is to be used as a two-component
developer, any kind of carrier may be selected and illustrative examples
include an iron powder, a ferrite powder, as well as carriers having a
styrene-acrylate copolymer, a silicone resin, etc. coated on the surfaces
of these powders.
The following examples are provided for the purpose of further illustrating
the present invention but are in no way to be taken as limiting.
Preparation of polyesters
The dicarboxylic acids and dialcohols shown in Table 1 (see below) were
charged into a four-necked round-bottom flask (capacity, 1 L) equipped
with a thermometer, a stainless steel stirrer, a nitrogen gas supply glass
pipe and a reflux condenser. The flask was set in a mantle heater and
heated, with an inert atmosphere being created in the flask by introducing
a nitrogen gas through the N.sub.2 supply pipe. Subsequently, 0.05 g of
dibutyltin oxide was added and reaction was carried out at a controlled
temperature of 200.degree. C. Thereafter, the polyvalent monomer having a
valence of 3 or more that is shown in Table 1 was added and further
reaction was performed in obtain polyesters.
The acid value (AV), hydroxyl group value (OHV), OHV+AV, OHV/AV ratio,
softening point (Tsp) and the glass transition point (Tg) of each of the
polyesters obtained were as shown in Table 1.
Preparation of a comparative polyester
A reaction vessel with a stirrer that was charged with 700 g of
polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl) propane and 97.2 g of
terephthalic acid was set in a mantle heater and heated, with an inert
atmosphere being created in the flask by introducing a nitrogen gas
through a N.sub.2 supply pipe. After adding 0.05 g of dibutyltin oxide,
reaction was performed at a controlled temperature of 200.degree. C. After
adding 156 g of anhydrous 1,2,4-benzenetricarboxylic acid, the reaction
was further continued, whereby a polyester resin having a softening point
of 120.degree. C. and a glass transition point of 58.degree. C. was
obtained (see Unexamined Published Japanese Patent Application No.
37353/1982).
TABLE 1-1
__________________________________________________________________________
Acid component
Poly- Aromatic
valent dicarboxylic
Alcohol component
monomer acid Aliphatic dialcohol
TMA TPA IPA
EG PG NPG 1,4-BD
DEG TEG
__________________________________________________________________________
Polyester
58 g 381 g
-- -- 170 g
-- -- -- 84 g
1 (12%)
(88%) (80%) (20%)
Polyester
77 g 315 g
-- -- -- 180 g
-- 89 g
--
2 (25%)
(75%) (70%) (30%)
Polyester
248 g
125 g
18 g
52 g
-- 155 g
25 g
-- --
3 (60%)
(35%)
(5%)
(30%) (60%)
(10%)
Polyester
31 g 416 g
-- 51 g
134 g
-- 12 g
-- --
4 (6%)
(94%) (30%)
(65%) (5%)
Polyester
58 g 381 g
-- 68 g
115 g
-- -- -- 21 g
5 (12%)
(88%) (40%)
(55%) (5%)
__________________________________________________________________________
TMA: anhydrous 1,2,4benzenetricarboxylic acid
TPA: terephthalic acid
IPA: isophthalic acid
EG: ethylene glycol
PG: propylene glycol
NPG: neopentyl glycol
1,4BD: 1,4butanediol
DEG: diethylene glycol
TEG: triethylene glycol
TABLE 1-2
__________________________________________________________________________
OHV AV OHV + AV
OHV/AV
TG TG
(KOH mg/g)
(KOH mg/g)
(KOH mg/g)
(-) (.degree.C.)
(.degree.C.)
__________________________________________________________________________
Polyester 1
20 35 55 0.6 62 141
Polyester 2
15 17 32 0.9 60 140
Polyester 3
50 28 78 1.8 57 135
Polyester 4
11 10 21 1.1 61 125
Polyester 5
11 31 42 0.4 59 144
Comparative
57 32 89 1.8 58 120
polyester 1
__________________________________________________________________________
Preparation of acid-modified PP
Acid-modified PP-1:
A low-molecular weight (Mn=4,000) (982 parts by weight) and 18 parts by
weight of maleic anhydride were dissolved and dispersed in 1,500 parts by
weight of xylene solvent under heating. Thereafter, 40 parts by weight of
dicumyl peroxide was added as a catalyst and the mixture was heated to the
boiling point of the solvent, at which temperature reaction was performed
for 4 h to obtain a maleic acid modified polypropylene.
Acid-modified PP-2 to PP-6:
Additional acid-modified PPs were prepared as above.
The characteristics of the thus prepared PP-1 to PP-6 of the present
invention, as well as those of comparative acid-modified polypropylenes
are shown in Table 2.
Using the polyesters and acid-modified PPs described above, 6 toners of the
present invention and 3 comparative toners were prepared (see Table 3) and
subsequently mixed with the carriers shown in Table 4 to fabricate
developers. The characteristics of these developers were then evaluated.
Preparation of toners
The toner components shown in Table 3 (polyester resin, release agent and
carbon black) were mixed by means of a V-type blender, melted and kneaded
with a twin-mill roll, then cooled, ground coarsely with a hammer mill,
ground finely with a jet mill, and finally classified with an air
classifier to prepare toner sample Nos. 1-6 having an average particle
size of 11.0 .mu.m. Each toner sample was finished by mixing with fine
silica particles.
Comparative toner sample Nos. 1-3 were prepared as described above using
the toner ingredients shown in Table 3.
Fabrication of developers
Each of the toners described above (72 parts by weight) was mixed with 1728
parts by weight of carrier sample Nos. 1-6 (see Table 4) in accordance
with the combinations shown in Table 5, whereby two-component developers
were fabricated.
The characteristics of these developers were evaluated by the methods
described below and the results are shown in Table 6.
TABLE 2
__________________________________________________________________________
Degree of Compressive
AV Density
Tsp
Melt index
penetration
Hardness
failure stress
-- Mn*
(mg KOH/g)
(g/cc)
(.degree.C.)
(cPs) (10.sup.-1 mm)
(-) (kg/cm.sup.2)
__________________________________________________________________________
Acid-modified PP-1
4000
18.0 0.89 148
600 0.1 71 129
Acid-modified PP-2
1500
35.7 0.88 139
190 0.3 62 104
Acid-modified PP-3
3000
18.1 0.89 144
133 0.3 58 90
Acid-modified PP-4
9000
10.2 0.90 150
3500 0.2 101 182
Acid-modified PP-5
600
48.1 0.88 131
20 1.8 52 55
Acid-modified PP-6
18000
6.4 0.91 159
8900 0.6 114 216
Biscol TS-200
3500
3.5 0.89 145
120 2 41 35
(Sanyo Chemical
Industries, Ltd.)
Biscol 660P
3500
0 0.89 145
70 1.5 46 53
(Sanyo Chemical
Industries, Ltd.)
__________________________________________________________________________
*Molecular weight of unmodified polypropylene
TABLE 3
__________________________________________________________________________
Binder resin
Release agent
Carbon black pH External additive
__________________________________________________________________________
Toner 1
Polyester 1
Acid-modified PP-1
Morgal L (Cabot Corporation)
3.0
R-805 (Nippon Aerosil Co.,
Ltd.)
(4 parts by weight)
(10 parts by weight)
(0.3 wt %)
Toner 2
Polyester 2
Acid-modified PP-2
PRINTEX 150T (Degussa AG)
5.0
R-972 (Nippon Aerosil)
(2 parts by weight)
(15 parts by weight)
(0.8 wt %)
Toner 3
Polyester 4
Acid-modified PP-3
RAVEN 1080 (Columbian)
2.4
R-805 (Nippon Aerosil)
(6 parts by weight)
(7 parts by weight)
(0.2 wt %)
Toner 4
Polyester 5
Acid-modified PP-4
Morgal L (Cabot Corporation)
3.0
R-805 (Nippon Aerosil)
(2 parts by weight)
(10 parts by weight)
(0.4 wt %)
Ethylene bisstearoamide
(2 parts by weight)
Toner 5
Polyester 3
Acid-modified PP-5
Morgal L (Cabot Corporation)
3.0
R-972 (Nippon Aerosil)
(2 parts by weight)
(12 parts by weight)
(0.2 wt %)
Toner 6
Polyester 1
Acid-modified PP-6
Morgal L (Cabot Corporation)
3.0
R-805 (Nippon Aerosil)
(15 parts by weight)
(10 parts by weight)
(0.6 wt %)
Comparative
Comparative
Acid-modified PP-1
Morgal L (Cabot Corporation)
3.0
R-805 (Nippon Aerosil)
toner 1
Polyester 1
(4 parts by weight)
(10 parts by weight)
(0.8 wt %)
Comparative
Polyester 1
Biscol TS-200
RAVEX 1080 (Columbian)
2.4
R-972 (Nippon Aerosil)
toner 2 (Sanyo Chemical
(15 parts by weight)
(0.4 wt %)
Industries, Ltd.)
Comparative
Polyester 1
Biscol 660P PRINTEX 150T (Degussa AG)
5.0
R-972 (Nippon Aerosil)
toner 3 (Sanyo Chemical
(7 parts by weight)
(0.6 wt %)
Industries, Ltd.)
__________________________________________________________________________
TABLE 4
______________________________________
Particle
Core size (.mu.m)
Resin coat
______________________________________
Carrier 1
Cu--Zn 80 Methyl methacrylate/
containing ferrite styrene copolymer
(60/40)
Carrier 2
Cu--Zn 120 Methyl methacrylate/
containing ferrite styrene copolymer
(60/40)
Carrier 3
Cu--Zn 60 Silicone resin (SR-2400
containing ferrite of Toray Silicone Co.,
Ltd.)
Carrier 4
Ni--Zn 80 Silicone resin (SR-2400
containing ferrite of Toray Silicone Co.,
Ltd.)
Carrier 5
Ni--Zn 40 Methyl methacrylate/
containing ferrite styrene copolymer
(70/30)
Carrier 6
iron 80 Methyl methacrylate/
styrene copolymer
(70/30)
______________________________________
TABLE 5
______________________________________
Toner Carrier
______________________________________
Developer
1 Toner 1 1
2 Toner 2 2
3 Toner 3 3
4 Toner 4 4
5 Toner 5 5
6 Toner 6 6
Comparative Comparative
1
developer 1 toner 1
Comparative Comparative
1
developer 2 toner 2
Comparative Comparative
1
developer 3 toner 3
______________________________________
TABLE 6
__________________________________________________________________________
Sticking
Hot offsetting
Cleaning quality Transfer
Toner Toner
temperature
temperature
10.sup.5
2 .times. 10.sup.5
Image
Fog efficiency
agglomeration
fusion
(.degree.C.)
(.degree.C.)
Initial
cycles
cycles
density
density
(%) (%) (wt
__________________________________________________________________________
%)
Developer 1
165 250< .largecircle.
.largecircle.
.largecircle.
1.21 0.001
94 3 0.009
Developer 2
160 250< .largecircle.
.largecircle.
.largecircle.
1.20 0.003
98 2 0.012
Developer 3
165 250< .largecircle.
.largecircle.
.largecircle.
1.24 0.002
91 8 0.015
Developer 4
165 250< .largecircle.
.largecircle.
.largecircle.
1.18 0.002
95 2 0.008
Developer 5
160 250< .largecircle.
.largecircle.
.largecircle.
1.05 0.008
88 10 0.056
Developer 6
175 250< .largecircle.
.largecircle.
.largecircle.
1.20 0.003
96 5 0.010
Comparative
205 210 .largecircle.
X X 0.68 0.031
52 46 0.208
developer 1
Comparative
185 220 .largecircle.
.DELTA.
X 0.80 0.020
61 33 0.195
developer 2
Comparative
185 225 .largecircle.
X X 0.52 0.058
40 62 0.340
developer 3
__________________________________________________________________________
Note: The developers fabricated in accordance with the present invention
performed satisfactorily without causing "toner filming" or the
photoreceptor.
Evaluation of fixability
1. Sticking temperature
A solid black and unfixed image was formed at the edge of receiving sheet
on U-Bix 5070 (Konica Corp.). The toner deposit was controlled at 1.0
mg/cm.sup.2.
The receiving sheet was passed through a fixing unit (for its
specifications, see Table 7 below), with the temperature of the upper roll
being lowered from 220.degree. C. by decrements of 5.degree. C., and the
temperature at which the receiving sheet started to stick to the upper
roll was designated as the "sticking temperature". The lower this
temperature, the better the performance of the toner used. The temperature
of the lower roll was set to be 20.degree. C. lower than the temperature
of the upper roll.
2. Hot offsetting temperature
A solid black and unfixed image (10 mm.times.10 mm) was formed on receiving
sheet on U-Bix 5070 (Konica Corp.). The toner deposit was controlled at
1.0 mg/cm.sup.2.
The receiving sheet was passed through a fixing unit (for its
specifications, see Table 7 below), with the temperature of the upper roll
being raised from 200.degree. C. by increments of 5.degree. C., and the
temperature at which hot offsetting started to occur was designated as the
"hot offsetting temperature". The higher this temperature, the better the
performance of the toner used. The temperature of the lower roll was set
to be 20.degree. C. lower than the the temperature of the upper roll.
TABLE 7
______________________________________
Upper roll dia. 60 mm
material of the perfluoroalkoxy resin
surface layer
Lower roll dia. 65 mm
material of the perfluoroalkoxy resin
surface layer
Nip width 9 mm
Time of residence in the nip
30 msec
Surface pressure 2 kgf/cm.sup.2
Others In the absence of both oil
applicator and cleaning member
______________________________________
Copying test with actual machine
Using an electrophotographic copier adapted from U-Bix 5070 (Konica Corp.)
that was equipped with an As-Se photoreceptor, a contact type magnetic
brush developer (for normal development), a hot pressure roll type fixing
unit, and a cleaning device having a urethane rubber cleaning blade, a
running test was conducted for a total of 2.times.10.sup.5 copying cycles
consisting of intermittent copying (a copying mode in which one copy was
taken for one sheet of document) and continuous copying. The copying
conditions were either is a hot and humid atmosphere (33.degree.
C..times.80% r.h.) or in a cold and dry atmosphere (10.degree.
C..times.20% r.h.). Similar results were attained under either conditions.
The results obtained in a hot and humid atmosphere are shown in Table 6 as
typical examples of evaluation.
1. Cleaning quality
The toner that remained on the surface of the photoreceptor after cleaning
and the fouling of image due to insufficient cleaning were visually
checked at the initial time and after copying through 10.sup.5 and
2.times.10.sup.5 cycles. The results were evaluated by the following
criteria.
______________________________________
Fouling of image due to
insufficient cleaning
Negative Positive
______________________________________
Residual toner
Negative .largecircle.
--
on photoreceptor
Positive .DELTA. X
______________________________________
2. Image density and fog density
The solid black area of each copy image (the area corresponding to a
document density of 1.3) and the white background (the area corresponding
to a document density of 0.0) were subjected to measurements of reflection
density with a Densitometer of Konica Corp. The results are designated
"image density" and "fog density", respectively.
Measurements on Developers 1-6 and Comparative Developers 1-3 at the
initial time were satisfactory: image density .gtoreq.1.30 and fog density
.ltoreq.0.005. Thus, only the results of measurements made after
2.times.10.sup.5 cycles are shown in Table 6.
3. Transfer efficiency
Transfer efficiency (%) was measured after 2.times.10.sup.5 cycles. This
parameter is express by:
##EQU1##
4. Toner agglomeration
After copying through 2.times.10.sup.5 cycles, a sample of the toner that
exactly weighed 2 g was taken out of the cleaning device and put into a
10-cc sampling tube. A specimen was prepared by tapping the sample tube
500 times in a Tapdenser (Seishin Kigyo Co., Ltd.). The specimen was left
to stand in a hot and dry atmosphere (60.degree. C..times.26% r.h.) for 2
h and sieved through the 48-mesh screen on a Powder Tester (Hosokawa
Micron Co., Ltd.) at an intensity of 4 for 30 sec. The percent toner
aggomeration was determined from the percent residual toner which was
calculated by the following equation:
##EQU2##
where a is the amount of residual toner in grams.
5. Toner fusion
The amount of toner fusion was measured by the following procedure:
(i) after copying through 2.times.10.sup.5 cycles, about 10 g of the
developer was sampled from the developing unit;
(ii) the developer was washed with water containing a surfactant, whereby
the statically deposited toner was removed;
(iii) the carrier in the toner sampled in step (i) was dried at 40.degree.
C. for 24 h and a portion of the dried carrier was measured in an amount
that exactly weighted 3 g;
(iv) the toner fused to the carrier was dissolved away with methyl ethyl
ketone, and the carrier was again dried at 40.degree. C. for 24 h to
measure its weight, a;
(v) the percent carrier coverage after 2.times.10.sup.5 cycles was
calculated by the following equation:
##EQU3##
(vi) the initial percent carrier coverage minus b was defined as the
amount of toner fusion.
As Table 6 shows, the developer samples fabricated in accordance with the
present invention exhibited satisfactory fixability (i.e., high resistance
to sticking and offsetting), developing quality, transferability,
cleanability, as well as good resistance to agglomeration and toner fusion
.
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